The present invention relates to a scroll-type fluid transferring machine provided with an oldham's coupling for effecting oscillation of an oscillatable scroll member.
First of all, before starting explanation of the scroll-type fluid transferring machine, the principle of the machine will be briefly described.
FIG. 3 shows structural elements essential to a scroll-type fluid transferring machine used as a compressing machine and the principle of compression. In FIG. 3, a reference numeral 1 designates a stationary scroll member, a numeral 2 designates an oscillatable scroll member, a numeral 3 designates an intake port, a numeral 4 designates an outlet port, a numeral 5 designates a compression chamber, and a symbol 0 designates the center of the stationary scroll member 1.
The stationary scroll member 1 has a wrap 1a and oscillatable scroll member 2 has a wrap 2a. The shape of the wraps 1a, 2a is the same, but the direction of winding is inverse. The wraps 1a, 2a are formed by an involute curve or combination of circular arcs as well known.
The operation of the structural elements of the machine will be described. The stationary scroll member 1 is kept still and the oscillatable scroll member 2 is assembled to the stationary scroll member 1 with 180.degree. phase-shifted condition so that the oscillatable scroll member is subjected to oscillation without rotation around the center O of the stationary scroll member 1. FIGS. 3a to 3d show relative movement of the stationary and oscillatable scroll members at angular positions of 0.degree., 90.degree., 180.degree. and 270.degree.. In the 0.degree. angular position shown in FIG. 3a, gas is confined in the intake chamber 3 so that the compression chamber 5 is formed between the wraps 1a, 2a. As the oscillatable scroll member 2 moves, the volume of the compression chamber 5 is gradually reduced thereby compressing the gas, and finally, the compressed gas is discharged through the outlet port 4 formed at the central portion of the stationary scroll member 1.
FIG. 5 is a cross-sectional view of a conventional scroll-type compressor applied to a totally closed type refrigerant compressor, as disclosed in Japanese Patent Application No. 64586/1984.
In FIG. 5, a reference numeral 1 designates the stationary scroll member in which the wrap 1a is formed in one side of a base plate 1b, a numeral 2 designates the oscillatable scroll member in which the wrap 2a is formed in one side of a base plate 2b, a numeral 3 designates the intake port (intake chamber), a numeral 4 designates the outlet port, a numeral 5 designates the compression chamber formed between the wraps 1a, 2a which are mutually combined, a numeral 6 designates a main shaft, a numeral 7 designates an oil cap which is provided with a suction opening 8 and which is attached to the lower end of the main shaft so as to cover the lower end with a predetermined space, and numerals 9, 10 designate bearing frames. The bearing frame 9 is provided with a recess 11 in which the oscillatable scroll member 2 is oscillatably received. As clearly shown in a cross-sectioned view of FIG. 4, an oldham's coupling 12 comprises an annular ring member 12a and each pair of first and second pawls 13, 14. The first paired pawls 13 are formed on the upper surface of the annular ring member 12a at diametrically opposing positions, and the second paired pawls 14 are formed on the lower surface of the ring member 12a at diametrically opposing positions so that a line extending between the first paired pawls orthogonally intersects a line extending between the second paired pawls 14. The first pawls are slidably put in a pair of first grooves 15 formed in the lower surface of the base plate 2b of the oscillatable scroll member 2, and the second pawls 14 are slidably put in a pair of second grooves 16 formed in the recess 11 of the bearing frame 9 as shown in FIGS. 4 and 5, whereby the oscillatable scroll member 2 is engaged with the bearing frame 9 so that it is subjected only to oscillation. The oldham's coupling 12 is of a shape such that when it is placed in a space defined by the base plate 2b of the oscillatable scroll member 2 and the bearing frame 9, air gaps which may be formed at contacting surfaces between the base plate 2b and the oldham's coupling 12 and between the bearing frame 9 and the oldham's coupling 12 are minimized, whereby the first space 17 formed at the inner circumferential side of the oldham's coupling 12 is isolated from the second space 18 formed at the outer circumferential side. An oil returning hole 19 is formed in the bearing frame 9 at a position inside the diameter of the oldham's coupling 12.
A reference numeral 20 designates a motor rotor, a numeral 21 designates a motor stator, a numeral 22 designates a shell, a numeral 23 designates an oil reservoir formed at the bottom of the shell 22, a numeral 24 designates an inlet pipe, a numeral 25 designates a discharge pipe, and a numeral 26 designates a bearing for the oscillatable scroll member which is eccentric to the axial center of the main shaft 6 and is placed in an eccentric hole 27 formed in an large diameter portion 6a of the main shaft 6. A shaft 2c extending from the lower surface of the base plate 2b of the oscillatable scroll member is rotatably fitted in the bearing 26. A numeral 28 designates a first main bearing for supporting the large diameter portion 6a of the main shaft 6, a numeral 29 designates a second main bearing for supporting a small diameter portion 6b of the main shaft 6, a numeral 30 designates a first thrust bearing for supporting the base plate 2b of the oscillatable scroll member 2. The first thrust bearing 30 is placed between the base plate 2b of the oscillatable scroll member 2 and the bearing frame 9 in the vicinity of the first main bearing 28 so as to support a portion near the center of the base plate 2b. A second thrust bearing 31 is placed between the lower surface of the large diameter portion 6a of the main shaft 6 and the upper surface of the bearing frame 10 so as to support the main shaft 6. An oil feeding port 32 is formed in the main shaft so as to be eccentric to and along the axial center of the main shaft 6 so that oil is fed through the opening 33 formed in the lower end of the main shaft 6 to the bearings 26, 29. A reference numeral 34 designates a gas vent hole formed in the main shaft 6 and a numeral 35 designates an oil returning hole formed in the bearing frame 10.
The stationary scroll member 1 is fastened to the bearing frames 9, 10 by bolts. A suitable fastening method such as press-fitting, shrink-fitting, screw-fitting and so on is used to fix the motor rotor 20 to the main shaft 6 and to fix the motor stator 21 to the bearing frame 10. The oil cap 7 may be fixed to the main shaft 6 by press-fitting or shrink-fitting.
The operation of the conventional scroll-type fluid transferring machine will be described.
When the motor rotor 20 is rotated, sliding movement of the first and second pawls 13, 14 of the oldham's coupling 12 is effected in the first and second grooves 15, 16 by means of the main shaft 6, whereby the oscillatable scroll member 2 is subjected to the oscillation of revolution, but not subjected to rotation; thus, compression of gas is initiated according to the principle of the operation as explained with reference to FIG. 3. In this case, a refrigerant gas is sucked in the shell 22 through the inlet pipe 24 and is passed through air gaps between the bearing frame 10 and the motor stator 21 and between motor rotor 20 and motor stator 21 as shown by solid arrow marks, whereby cooling of the motor is effected. The refrigerant gas is then passed through an air gap between the shell 22 and the bearing frames 9, 10 to be sucked in the compression chamber 5 through the intake port 3 formed in the stationary scroll member 1. The refrigerant gas compressed in the compression chamber 5 is discharged from the compressor through the outlet port 4 via the discharge pipe 25.
A lubricating oil is supplied from the oil reservoir 23 through the oil cap 7 and the oil feeding port 32 provided in the main shaft 6 to the bearings 26, 29 by the function of a centrifugal pump to effect lubrication of the bearings 26, 29, followed by lubricating of the bearings 28, 30 and 31. The lubrication oil is then returned to the oil reservoir 15 through the oil returning holes 19, 35 formed in the bearing frames 9, 10. As an expedient for preventing the lubricating oil which has lubricated the bearing 31 and so on from being sucked into the intake port 3, a contacting area is provided between the upper surface of the oldham's coupling ring 12 and the lower surface of the base plate 2b of the oscillatable scroll member 2, and the gap formed in the contacting area is minimized. Further, the intake port (intake chamber) 3 is isolated from sliding elements by minimizing the gaps in the contacting area of the pawls 13, 14. The gas vent hole 34 formed in the main shaft 6 increases pump efficiency by quickly discharging the gas in the oil gap 7 outside the shaft during the operations of the machine.
In order to avoid a reduction in performance of the scroll-type fluid transferring machine, it is desirable to minimize the pressure loss at the intake port formed at the outer circumferential part of the stationary scroll member 1. However, when the scroll-type machine is used as a compressor for air-conditioning or refrigerating in which a refrigerant is contained, retention of the refrigerant in the shell is inavoidable. When the scroll-machine is turned on in the presence of the refrigerant in the shell, there results an abnormal rise in a discharging pressure which can cause breakage of the compressor or otherwise actuation of a safety device, a pressure switch and so on to protect a piping circuit for the compressor. For this reason, it is also desirable to increase the pressure loss at the intake port. The above-mentioned requirements contradict each other, and therefore one has to be sacrificed. In the case that the pressure loss in the intake port is made greater, a fluid pressure between the wraps becomes lower than the inner pressure of the shell by the magnitude corresponding to the pressure loss, with the consequence that the lubricating oil which has lubricated the bearings under a pressure substantially same as the inner pressure of the shell and has flowed into the first space 17 of the recess 11 of the bearing frame 9 is easily taken into the compression chamber via second space 18 thereby increasing an oil consumption.